RESULTS OF BRITISH TRANSIT EXPEDITION'S. 61 



moment the central sun, the earth, and the earth's path, not 

 as they really are, for the mind refuses altogether to picture 

 the dimensions even of the earth, which is but an atom com- 

 pared with the sun, whose own proportions, in turn, mighty 

 though they are, sink into utter insignificance compared with 

 the enormous scale of the orbit in which the earth travels around 

 him. Let us reduce the scale of the entire system to one 

 5oo-millionth part of its real value: even then we have a 

 tolerably large orbit to imagine. We must picture to our- 

 selves a fiery globe 3 yards in diameter to represent the sun, 

 and the earth as a one-inch ball circling round that globe at 

 a distance of about 325 yards, or about 350 paces. The 

 diameter of the earth's orbit would on this scale, therefore, 

 be somewhat more than a third of a mile. If we imagine 

 the one-inch ball moving round the fiery globe once in a 

 year, while turning on its axis once in a day, we find our- 

 selves under a difficulty arising from the slowness of the 

 resulting motions. We should have found ourselves under 

 a difficulty arising from the rapidity of the actual motions if 

 we had considered them instead. The only resource is to 

 reduce our time-scale, in the same way that we have reduced 

 our space -scale : but not in the same degree ; for if we did 

 we should have the one-inch ball circling round its orbit, a 

 third of a mile in diameter, sixteen times in a second, and 

 turning on its axis five thousand times in a second. Say, 

 instead, that for convenience we suppose days reduced to 

 seconds. Then we have to picture a one-inch globe circling 

 once in rather more than six minutes about a globe of fire 3 

 yards in diameter, one-sixth of a mile from it, and turning 

 on its axis once in a second. We must further picture the 

 one-inch globe as inhabited by some 1,500 millions of crea- 

 tures far too small to be seen with the most powerful micro- 

 scope in fact, so small that the tallest would be in height 

 but about the seven-millionth of an inch and we must 

 imagine that a few of these creatures undertake the task of 

 determining from their tiny home swiftly rotating as it rushes 

 in its orbit around a large globe of fire, 325 yards from them 



